Stern arrangement for a ship

ABSTRACT

A stern arrangement for a ship where the stern of the ship is made modifiable or convertible for at least two different purposes by moving or by replacing at least a part of the stern. The stern of the ship is convertible to be a towing notch or to be equipped with a stern roller. The invention provides an icebreaker which is equipped with a towing notch in wintertime and with a stern roller in the summertime for open water operations.

The present invention relates to a stern arrangement for a ship.

BACKGROUND OF THE INVENTION

There are occasions when a ship is towed by another ship. Typically ithappens when an icebreaker tows a ship. Towing by icebreaker must bedone so that the bow of the ship to be towed has been pulled tightlyinto the close contact with the stern of the icebreaker. The ship to betowed will be kept in the right place by a towing winch located aboardon the icebreaker. The winch pulls strongly at the wire rope the bow ofthe towed ship against the stern of the icebreaker during the towingoperation.

For towing purposes the stern of the icebreaker must be formed in aspecial way. At the stern of the icebreaker there is an inwards curvedtowing notch which makes possible to tow another vessel. Only whenequipped with this notch it is possible for the icebreaker to tow a shipin the way that the bow of the ship to be towed is pressed directlytowards the stern of the icebreaker.

There are also other kind of special needs for the stern form of a ship.In open water for example the anchor handling and the cable layingoperations require different kind of stern forming. At the stern of asupply vessel there must not be any formed towing notches. Instead ofthat it is on the contrary required that the stern of the supply vesselis straight and the stern roller is installed. In the supply vessel thedifferent kind of hoisting operations are done over the transom with awinch or crane.

The special requirements said above cause that a ship constructed forone purpose can not be used for another purpose. The same ship can notbe used for the towing in winter and for supply operations in summer.The requirements for the stern shape and the stern structure are sodifferent in winter operations and respectively in summer operationsthat it is not possible to build a fixed structure which would besuitable for the both purposes.

The problem with icebreakers, however, is their short operating time inwinter. It should be able to use icebreakers also in the summertime inopen water. Correspondingly the supply vessel can not be used for towingin wintertime because of its unsuitable stern construction.

SUMMARY OF THE INVENTION

The object of the present invention is to eliminate the above mentionedproblem. This purpose will be achieved so that according to theinvention the stern of the ship is made modifiable or convertible for atleast two different purposes, by moving or by replacing at least a partof the stern.

PREFERRED EMBODIMENTS OF THE INVENTION

According to a preferred embodiment of the invention the stern of theship is convertible to be a towing notch or to be equipped with a sternroller.

The preferred embodiment of the invention provides the ship which isequipped with a structure which enables a towing notch in wintertime anda stern roller in the summertime. Combining these two possibilities itis for the first time possible to make a multipurpose icebreaker whichis suitable both for winter operations and also for summer operations.

Besides the supply operations in summer the suitable tasks for amultipurpose icebreaker would be for example towing, anchor handling,cable laying, flexible pipe laying and supply operations. These kind ofoperations are usually operated by a special supply ship which has thestraight stern and which is also equipped with a stern roller. With asupply ship it is possible to do different kind of hoisting operationsover the transom with a winch or crane. Typical operations are anchorhandling and hoisting of umbilicals and other offshore equipments.

According to an embodiment of the invention at the stern of the shipthere is at least one movable part which moves out in the way that atowing notch or a stern roller is available.

An other embodiment of the invention the stern of the ship is equippedeither with a fixed towing notch or with a fixed stern roller section,and the other one of them is movable or removable in the way that thetowing notch or the stern roller is available for use one at a time.

Still one embodiment of the invention is that the towing notch and thestern roller section are both removable, and at the stern of the shipthere is a place where the towing notch or the stern roller can beinstalled one at a time.

The above and other features and advantages of this invention willbecome better understood by reference to the detailed description thatfollows, when considered in connection with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic side view of the stern of the towing ship and thebow of the ship to be towed.

FIG. 2 is a schematic side view of the ship of FIG. 1 with the modifiedstern construction.

FIG. 3 is a top view of the stern of the ship of FIG. 3.

FIG. 4 is an aft view of the stern construction of the ship of FIG. 2.

FIG. 5 is a side view of the stern construction of the ship of FIG. 2according to the second embodiment.

FIG. 6 is the stern construction of the ship of FIG. 2 according to thethird embodiment.

FIG. 7 is the stern construction of the ship of FIG. 2 according to thefourth embodiment.

FIG. 8 shows the function of the stern construction of FIG. 7.

FIG. 9 is the stern construction of the ship of FIG. 2 according to thefifth embodiment.

FIG. 10 is the stern construction of the ship of FIG. 2 according to thesixth embodiment.

FIG. 11 is a top view of the stern construction of the ship of FIG. 10.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

FIG. 1 is a schematic side view of the stern of the towing ship 10 andthe bow of the ship 20 to be towed. In the FIG. 1 the bow 21 of the ship20 has been drawn against the stern notch 12 of the ship 10 by pullingat the wire rope 11. In icebreaker use the towing notch 12 is equippedwith rubber fenders 13 on both sides and a steel casting or a steelplate at the bottom of the notch 12.

The stern of the towing ship 10 in FIG. 1 has been formed in the waythat the notch 12 is below the working deck level and that there is aclearance 15 between the aft deck 16 and the bow 21 of the ship 20 to betowed. If the towed ship 20 has a bulbous bow 22 there must also be aclearance 17 for that.

In FIG. 2 is a schematic side view of the ship 10 of FIG. 1 with themodified stern construction. Above the notch 12 in close contact thereis a separate steel section 30 with a stern roller 31 added. The uppersurface of the section 30 is fitted to be on the same level with the aftworking deck 16 so that the section 30 and the deck 16 together form anordinary looking supply ship stern. The wire rope 11 can now easily beused for hoisting and for anchor handling operations.

The section 30 has been built and reinforced according to the workingdeck load requirements. It can be lifted on its place for use in summerand removed again for wintertime. The joint of the stern section can bemade by welding the section 30 to the aft working deck 16 or it can beattached by bolts 33. There may also be guide members 32 to help theinstallation of the section 30 and to help locking the section into itsright place.

The notch 12 may also be a removable section instead of the rollersection 30. In that case the roller section 30 may be formed to be afixed part of the aft working deck. Still another embodiment of the shipis that the both sections are removable. Into the ship will then beinstalled the section which will be needed at that time.

FIG. 3 is a top view of the stern of the ship 10 of FIG. 2. The section30 with a stern roller 31 is installed to the stern of the icebreaker.The section 30 is located above the notch 12 so that the stern of theship forms a straight line instead of the notch.

Alternatively the construction of FIG. 3 can also be arranged so that atthe stern of the ship 10 there is only a place for an external section.Then depending of the needed operation either the notch section 12 orthe stern roller section 30 will be selected and installed into thatplace.

This arrangement is suitable especially when the ship is so low that thenotch section 12 and the stern roller section 30 can not be installedtogether one on the other. Also the stern roller 31 of very largediameter does not allow the roller section 30 and the notch 12arrangement to be installed together at the same time.

The stern roller section 30 in FIG. 3 may also be narrower so that itcovers only a part of the notch section 12. In that case the rubberfenders 13 extend further aft and a part of the notch will be seentogether with the roller arrangement.

FIG. 4 is an aft view of the stern construction of the ship 10 of FIG.3. The removable section 30 with a roller 31 is installed to the sternof the icebreaker above the notch 12. The rubber fenders 13 of thetowing notch 12 can be seen on both sides and also the steel casting orsteel plate 14 at the bottom of the notch.

FIG. 5 is a side view of the stern construction of the ship according tothe second embodiment. The roller section 30 is provided with horizontalguide members and with a hydraulic cylinder 34. The cylinder 34 pushesthe section 30 out when it will be needed and respectively pulls it backagain below the aft deck 16 when the notch 12 is needed in icebreakeruse.

In FIG. 6 is the third embodiment for the stern construction of the ship10. The roller section 30 is provided with guide members and a hydrauliccylinder 34 which are lined together with the bottom line of the ship10.

FIG. 7 is the stern construction according to the fourth embodimentwhere the stern roller 31 section 30 can be turned to a store locker 35while the vessel is used as an icebreaker. The store locker 35 is formedinto the working deck 16 and it is provided with a cover 36.

In FIG. 8 is presented the function of this stern construction of FIG.7. The cover 36 has been opened and the section 30 will be turned aroundthe axis 37 into the locker 35. When the roller section 30 is in thelocker 35 and the cover 36 is closed the ship 10 can be used as anicebreaker.

FIG. 9 is the stern construction according to the fifth embodiment wherethe stern roller section 30 is located on rails 38. When the section 30will be installed it will be lifted on the rails 38. After gliding alongthe rails 38 the section 30 will be stopped by the stoppers and theconical locking members will lock it into the place. There may also bebolts or hydraulic locking members at fore end of the rails 38.

In FIG. 10 is the stern construction of the ship 10 where the notchsection 12 is moving instead of the roller section 30. The notch 12 maybe even removable but in this embodiment the stern roller 31 is fixed.The notch will be moved by a hydraulic cylinder 34. The final locking ismade by hydraulic cylinders or preferably by bolts. FIG. 11 shows thetop view of the same construction.

We claim:
 1. A convertible stern arrangement for a ship comprising:astern; an inwardly curved towing notch formed in said stern forreceiving a bow of a ship to be towed; a removable section disposed insaid towing notch; and a stern roller for use in hoisting operationsmounted on said removable section, whereby said stern is suitable foruse in hoisting operations and can be converted for use in towingoperations by removing said removable section.
 2. The stern arrangementfor a ship of claim 1, wherein the removable section fills in the towingnotch such that the stern includes a substantially straight section. 3.The stern arrangement for a ship of claim 2, wherein the towing notch isbelow a level of a working deck and an upper surface of the removablesection is at the level of the working deck.
 4. A convertible sternarrangement for a ship comprising:a stern; an inwardly curved towingnotch formed in said stern for receiving a bow of a ship to be towed; amovable section disposed in said stern, said movable section beingmovable to fill in at least a portion of said towing notch; and a sternroller for use in hoisting operations mounted on said movable section,whereby said stern is suitable for use in towing operations and can beconverted for use in hoisting operations by moving said movable section.5. The stern arrangement for a ship of claim 4, wherein the movablesection fills in the towing notch such that the stern includes asubstantially straight section.
 6. The stern arrangement for a ship ofclaim 4, wherein the movable section is disposed below a working deckwhen not in use.
 7. The stern arrangement for a ship of claim 4, whereinthe movable section is moved by a hydraulic cylinder.
 8. The sternarrangement for a ship of claim 4, wherein a storage locker for storingthe movable section when not in use is formed below the working deck, acover for said locker is provided in the working deck, and the movablesection is pivotally attached to a base so that the movable section canbe swung into and out of said locker.
 9. The stern arrangement for aship of claim 4, wherein the movable section is mounted on rails.
 10. Aconvertible stern arrangement for a ship comprising:a stern having asubstantially straight section; a stern roller for use in hoistingoperations fixedly mounted at said stern; and a movable section disposedin said stern, said movable section having an inwardly curved towingnotch formed therein and being movable in a direction away from saidstern so as to extend beyond said stern roller, whereby said stern issuitable for use in hoisting operations and can be converted for use intowing operations by moving said movable section.
 11. The sternarrangement for a ship of claim 10, wherein the stern roller is mountedabove the movable section.
 12. The stern arrangement for a ship of claim10, wherein the movable section is moved by a hydraulic cylinder.